mtd: jedec_probe: fix NEC uPD29F064115 detection

linux v2.6.31-rc6 can not detect NEC uPD29F064115.

uPD29F064115 is a 16 bit device.
datasheet:
  http://www.cn.necel.com/memory/cn/download/M16062EJ2V0DS00.pdf

This applies the same fix as used for SST chips in commit 
ca6f12c6

 ("jedec_probe: Fix SST 16-bit 
chip detection").

Signed-off-by: Hiroshi Ito <ito@mlb.co.jp>
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>